Effects of barium substitution on the sintering behavior, dielectric properties of Ca2Nb2O7 ferroelectric ceramics

Abstract

Barium-doped Ca2Nb2O7 ceramics were prepared in the form of Ca2-xBaxNb2O7 (0 ≤ x ≤ 0.6) by solid-state reaction. The solubility limit of barium in Ca2Nb2O7 was found to be x = 0.4 based on X-ray diffraction and Raman spectroscopy analysis. When x ≤ 0.4, Ca2-xBaxNb2O7 solid solutions with a monoclinic perovskites-like layered structure (PLS) were formed, whereas beyond x = 0.4, a secondary phase CaNb2O6 was detected. The dielectric properties obviously depended on the barium substitution. With increasing barium amount, the dielectric constant increased from 33.5 for pure Ca2Nb2O7 to 38.6 for x = 0:4 (f = 1 MHz). The Curie temperature (Tc) of the x = 0.1 sample was 1280±5°C. The phase transition was confirmed to be the second order.